Pawl-ratchet wheel assembly in a timepiece



Nov. 17, 1970 M. HETZEL 5 PAWL-RATCHET WHEEL ASSEMBLY IN A TIMEPIECEFiled July so, 1968 TRANSDUCER United States Patent 3,540,205PAWL-RATCHET WHEEL ASSEMBLY IN A TIMEPIECE Max Hetzel, Biel,Switzerland, assignor to Centre Electrouique Horloger S.A., Neuchatel,Switzerland, a company of Switzerland Filed July 30, 1968, Ser. No.748,666 Claims priority, application Switzerland, Aug. 22, 1967, 11,799/69 Int. Cl. G04c 3/00 US. Cl. 5823 Claims ABSTRACT OF THE DISCLOSURE Thepresent invention relates to a pawl-ratchet wheel assembly forelectro-mechanical timepieces whose time base and motor are constitutedby a mechanical resonator which is electrically maintained. The pawl andratchet assembly comprises a driving pawl driving a ratchet wheel in onedirection, a return pawl preventing a rotation of the ratchet wheel inthe opposite direction and a device for adjusting the relative phase ofthe driving and return pawls.

Already known in the prior art is a pawl-ratchet wheel assembly for anelectro-mechanical watch whose time base comprises a mechanicalresonator carrying a driving pawl acting on a ratchet wheel whoserotation in the opposite direction is prevented by a return pawl andcomprising a device operative to adjust the pressure of the return pawland which operates at a relatively low frequency.

It has been found however that in the pawl-ratchet wheel devices usedfor transforming high frequency mechanical oscillations into rotationalmovement that the adjustment of the pressure of the return pawl on theratchet wheel does not constitute a suihcient adjustment and hence, thatit would be desirable to provide a device for adjusting the relativephase of the ends of the pawls.

The adjustment of the relative phase of the pawls should preferably takeplace independently of the adjustment of the pawl pressure. This meansthat once the relative phase is adjusted, it cannot be modified by asubsequent adjustment of the pawl pressure.

To this effect, there has been proposed a construction in which thedevice for adjusting the relative phase of the pawls acts on the returnpawl by moving this return pawl tangentially to the ratchet wheel. Inthis assembly, the device for adjusting the pressure of the return pawlis independent of the phase adjustment. While this construction givessatisfactory results, it is however complicated and costly.

The present invention has for its primary objective to provide apawl-ratchet wheel assembly having means for adjusting the relativephase of the pawls and which is of a simple construction and thereforeeasier to manufacture on a large scale.

The pawl-ratchet wheel assembly of the present invention is particularlydesigned for electro-mechanical timepieces whose time base and drivingmember are constituted by a mechanical resonator which is electricallymaintained. 'Ihe pawl and ratchet wheel comprises a driving pawl drivinga ratchet wheel in a given direction, a return pawl preventing rotationof the ratchet wheel in the opposite direction and a device foradjusting the relative phase of the driving and return pawls. The devicefor adjusting the phase acts on the ratchet wheel in such a way that theratchet wheel moves with the return pawl relative to the driving pawl.

The accompanying drawing represents by way of example one embodiment ofthe subject of the invention.

The single figure of the drawing schematically represents, in partialsection, an electro-mechanical timepiece movement comprising essentiallya mechanical resonator 1 secured by its foot 1a on a plate 2. Theresonator comprises two oscillating branches lb and 10 which areelectrically maintained by means of transducers. Branch lb carries adriving pawl 3 which is not directly embedded in a branch of theresonator, but rather is mounted in a rectangular bar 4 secured on theresonator by means of a pin 5 located at one end of bar 4 in order to beable to rotationally move under the action of a lateral force exerted onthe free end of the bar. The driving pawl engages in the teeth of aratchet wheel 6 whose pinion 7 is constituted by a polarized polar wheelmagnetically driving a magnetic wheel 8 whose pinion 9 meshes with afirst intermediate wheel 10 which is connected to drive the other gearsof the timepiece movement.

Instead of a magnetic driving, it would also be possible to provide amechanical driving, such as by a toothed wheel.

Wheels 6 and 8 are pivoted in an auxiliary cage constituted by twobridge plate members 11 and 12 secured, respectively, on the upper andlower sides of foot 1a of the resonator.

The lower bridge plate member 12 is of simple form while the upperbridge plate member 11 has a more complicated shape including cut-outsor slots 16 and 18 whose two sides are connected, respectively, byadjusting screws 17 and 19. The purpose of the slots 16 and 18 is torender the plate member 11 flexible, as described in more detail below.The return pawl 14 is embedded at an end portion 20 of the plate 11which can be 'bent or flexed by screw 19 to adjust the pressure of thereturn pawl. Screw 17 serves to adjust the relative phase of the end ofthe pawl as will be described later.

The upper bridge plate member 11 is divided by the slot 16 into twoZones, a foot portion 11a secured to the foot of the resonator by ascrew and two positioning pins 13 and 15 and a free zone portion 1111connected to foot 11a by an elastically deformable portion 110. The endportion 20 is integral with the free Zone 111:- and moves therewith whenadjusting screw 17 is acted upon.

In operation, the screw 17 is either tightened or loosened to eifectpivotal movement of the free zone portion 11b of the plate member 11either towards or away from the stationary foot portion 11a. Themovement of the free zone portion 11b carries with it both the ratchetwheel 6 and the return pawl 14 and hence, by merely adjusting the screw17, the phase relationship between the drive pawl 3 and the return pawl14 is selectively adjusted. When the free zone portion 11b is moved, theaxis of the ratchet wheel is then no longer exactly perpendicular to thetrajectory of the driving pawl. It has been proven however that thiscondition is not absolutely necessary for a proper functioning of theassembly. However during oblique movement of the axis of the ratchetwheel, the ratchet wheel must be moved relative to the driving pawl insuch a way that the relative movement of the ratchet wheel and of thedriving pawl at their contact point be a tangential movement. It is forthis reason that in the particular case where the ratchet wheel and itspinion are pivoted between the two bridge plate members that the devicefor adjusting the phase has been provided on the bridge which is nearestto the ratchet wheel, in this instance, the upper bridge plate member.

The pivoting point of the movable, free zone portion 11b of bridge platemember 11 located in part 110 is at least approximately on a lineconnecting the contact point of the driving pawl on the ratchet wheeland the axis of this ratchet wheel. The axis of gear 8 driven by thepinion of the ratchet wheel is preferrably located near the pivotingpoint of the free zone portion 11b, and the position of this gear willbe practically unchanged during movement of the ratchet wheel.

The bridge plate member 11 carrying all the means for adjusting theassembly can thus be easily manufactured, as for example, by stamping.

What is claimed is:

1. A pawl and ratchet assembly for an electromechanical timepiececomprising: a rotatably mounted toothed ratchet wheel; a drive pawl; anelectrically maintained mechanical resonator; means mounting said drivepawl on said resonator to effect intermittent rotation of said ratchetwheel in a given direction in response to vibrational movement of saidresonator; a return pawl operative to prevent rotation of said ratchetwheel in a direction opposite to said given direction; and variablysettable mounting means mounting said ratchet wheel and return pawl formovement together relative to said drive pawl to variably set the phaserelationship between said drive and return pawls.

2. An assembly according to claim 1; wherein said variably settablemounting means comprises a plate member, means mounting said ratchetwheel for rota tional movement on one portion of said plate member,means mounting said return pawl on said one portion of said plate memberin releasable engagement with said ratchet wheel, means for renderingsaid one portion of said plate member movable with respect to theremaining portion of said plate member, and means for selectivelyvarying the movement of said one portion with respect to said remainingportion to effect movement of both said ratchet wheel and return pawlrelative to said drive pawl.

3. An assembly according to claim 2; wherein said means for renderingsaid one portion of said plate member movable with respect to theremaining portion of said plate member comprises means defining a slotin said plate member dividing same into said one portion and remainingportion and effective to render said plate member flexible, and whereinsaid means for selectively varying the movement of said one portion withrespect to said remaining portion comprises means for selectivelyvarying the dimension of said slot to effect movement of said oneportion towards and away from said remaining portion.

4. An assembly according to claim 3; wherein said slot extends inwardlytowards the center of said plate member, and wherein said means forselectively varying the dimension of said slot comprises screw meansoperative to effect pivotal movement of said one portion about a pointlocated in said remaining portion in the vicinity v of the innermostextension of said slot.

5. An assembly according to claim 3; further including means on saidplate member for adjusting the contact pressure between said return pawland ratchet wheel.

References Cited UNITED STATES PATENTS 3,446,006 5/1969 Frossard et a1.5823 RICHARD B. WILKINSON, Primary Examiner E. C. SIMMONS, AssistantExaminer US. Cl. X.R. 58-116; 310-37

